There are known in the art charged particle beam devices. For example, scanning electron microscopes are disclosed in U.S. Pat. No. 5,659,172 of Wagner which describes a method for reliable defect detection using multiple perspective Scanning Electron Microscope (SEM) images. A SEM usually includes an electron gun for generating an electron beam, a SEM lens system for focusing and converging the electron beam, a deflection coil for deflecting the electron beam, a detector for detecting electrons, such as secondary emitted electrons or reflected electrons that are emitted/reflected from an object and a processor that is operative to construct SEM images in response to detection signals provided from the detector. Usually, the electron gun, the SEM lens system and the deflection coil are located within a column, which is commonly referred to as SEM column. The resolution of a SEM and its power consumption are inversely proportional to the distance between the SEM column and the object. This distance is also referred to as a working distance. The detector can also be placed within the SEM column.
Another type of known Charged particle beam device is the Focused ion beam (FIB) device. FIB systems are generally utilized to perform die milling and cross sectioning. The milled or cross sectioned die is usually analyzed by an inspection device, such as a SEM, to detect defects. FIB systems can also be utilized to generate FIB images. FIB systems include an ion source for generating an ion beam, a FIB lens system for focusing the ion beam to provide a focused ion beam and an ion beam deflector for deflecting the focused ion beam. A FIB system that is operative to generate a FIB image also has a detector and a processor. Usually, the ion source, the FIB lens system and the ion beam deflector are located within a column, which is commonly referred to as FIB column. The detector can also be placed within the FIB column.
SEM images are generated by irradiating an object with an electron beam, collecting signals resulting from an interaction of the electron beam with at least one portion of the object and processing the collected signals. FIB images are generated in a similar analogues manner, except that the object is irradiated with a focused ion beam.
Systems that include both FIB and SEM systems are known in the art and are referred to as FIB/SEM systems. SEM system allows to inspect a surface of an inspected object, such as a surface of a multi layered die. FIB systems allow for milling the surface and exposing inner layers to inspection. Usually, after the FIB mills the die, the SEM system is utilized to inspect the revealed layers and to further analyze the milled die for detecting defects.
There are known in the art other types of Charged particle beam devices such as Transmission Electron Microscope (TEM), and Scanning Transmission Electron Microscope (STEM).
Calibrating column parameters of a charged particle beam device is essential in order to obtain an optimal spot on the target surface (wafer). The characteristics of optimal spot are, for instance, spot size and how round and symmetric is the spot and it means whether the spot has astigmatism deviations for the x and y axes. When using high current beam, say ≧1 nA, the spot is milled into the substrate, or in other words the process is destructive. In the case that the so milled spot is not optimal, it would be desired to adjust the operational parameters for generating a better spot. However, since the generation of the spots is “destructive” hampers, subsequent attempts to generate spots using possibly other parameters. The reason is that, when a high current beam is used, the resulting image is, in many cases, not clear, thereby hindering to inspect and determine the characteristics of the resulting spot.
Accordingly, the process of calibrating the operational parameters of high beam current charged particle beam device (such as FIB) is, in many cases, manual and time-consuming. It also strongly depends on the skills of the technician who performs the task, and therefore the quality of the resulting calibration process may vary from one individual to the other.
There is, thus a need in the art to provide for a new system and method facilitating calibration of column parameters of Charged particle beam devices, in particular those operating in high current.